Archives for 2015

Today I read a paper titled “Estimating 3D Human Shapes from Measurements”

The abstract is:

The recent advances in 3-D imaging technologies give rise to databases of human shapes, from which statistical shape models can be built.

These statistical models represent prior knowledge of the human shape and enable us to solve shape reconstruction problems from partial information.

Generating human shape from traditional anthropometric measurements is such a problem, since these 1-D measurements encode 3-D shape information.

Combined with a statistical shape model, these easy-to-obtain measurements can be leveraged to create 3D human shapes.

However, existing methods limit the creation of the shapes to the space spanned by the database and thus require a large amount of training data.

In this paper, we introduce a technique that extrapolates the statistically inferred shape to fit the measurement data using nonlinear optimization.

This method ensures that the generated shape is both human-like and satisfies the measurement conditions.

We demonstrate the effectiveness of the method and compare it to existing approaches through extensive experiments, using both synthetic data and real human measurements.

Today I read a paper titled “Virtual Texturing”

The abstract is:

In this thesis a rendering system and an accompanying tool chain for Virtual Texturing is presented.

Our tools allow to automatically retexture existing geometry in order to apply unique texturing on each face.

Furthermore we investigate several techniques that try to minimize visual artifacts in the case that only a small amount of pages can be streamed per frame.

We analyze the influence of different heuristics that are responsible for the page selection.

Alongside these results we present a measurement method to allow the comparison of our heuristics.

Today I read a paper titled “A Behavior-based Approach for Multi-agent Q-learning for Autonomous Exploration”

The abstract is:

The use of mobile robots is being popular over the world mainly for autonomous explorations in hazardous/ toxic or unknown environments.

This exploration will be more effective and efficient if the explorations in unknown environment can be aided with the learning from past experiences.

Currently reinforcement learning is getting more acceptances for implementing learning in robots from the system-environment interactions.

This learning can be implemented using the concept of both single-agent and multiagent.

This paper describes such a multiagent approach for implementing a type of reinforcement learning using a priority based behaviour-based architecture.

This proposed methodology has been successfully tested in both indoor and outdoor environments.

Today I read a paper titled “Attraction-Based Receding Horizon Path Planning with Temporal Logic Constraints”

The abstract is:

Our goal in this paper is to plan the motion of a robot in a partitioned environment with dynamically changing, locally sensed rewards.

We assume that arbitrary assumptions on the reward dynamics can be given.

The robot aims to accomplish a high-level temporal logic surveillance mission and to locally optimize the collection of the rewards in the visited regions.

These two objectives often conflict and only a compromise between them can be reached.

We address this issue by taking into consideration a user-defined preference function that captures the trade-off between the importance of collecting high rewards and the importance of making progress towards a surveyed region.

Our solution leverages ideas from the automata-based approach to model checking.

We demonstrate the utilization and benefits of the suggested framework in an illustrative example.

Today I read a paper titled “Algorithms for two variants of Satisfaction Approval Voting”

The abstract is:

Multi-winner voting rules based on approval ballots have received increased attention in recent years.

In particular Satisfaction Approval Voting (SAV) and its variants have been proposed.

In this note, we show that the winning set can be determined in polynomial time for two prominent and natural variants of SAV.

We thank Arkadii Slinko for suggesting these problems in a talk at the Workshop on Challenges in Algorithmic Social Choice, Bad Belzig, October 11, 2014.

Today I read a paper titled “Immersive and Collaborative Data Visualization Using Virtual Reality Platforms”

The abstract is:

Effective data visualization is a key part of the discovery process in the era of big data.

It is the bridge between the quantitative content of the data and human intuition, and thus an essential component of the scientific path from data into knowledge and understanding.

Visualization is also essential in the data mining process, directing the choice of the applicable algorithms, and in helping to identify and remove bad data from the analysis.

However, a high complexity or a high dimensionality of modern data sets represents a critical obstacle.

How do we visualize interesting structures and patterns that may exist in hyper-dimensional data spaces? A better understanding of how we can perceive and interact with multi dimensional information poses some deep questions in the field of cognition technology and human computer interaction.

To this effect, we are exploring the use of immersive virtual reality platforms for scientific data visualization, both as software and inexpensive commodity hardware.

These potentially powerful and innovative tools for multi dimensional data visualization can also provide an easy and natural path to a collaborative data visualization and exploration, where scientists can interact with their data and their colleagues in the same visual space.

Immersion provides benefits beyond the traditional desktop visualization tools: it leads to a demonstrably better perception of a datascape geometry, more intuitive data understanding, and a better retention of the perceived relationships in the data.

Today I read a paper titled “A Self-Supervised Terrain Roughness Estimator for Off-Road Autonomous Driving”

The abstract is:

We present a machine learning approach for estimating the second derivative of a drivable surface, its roughness.

Robot perception generally focuses on the first derivative, obstacle detection.

However, the second derivative is also important due to its direct relation (with speed) to the shock the vehicle experiences.

Knowing the second derivative allows a vehicle to slow down in advance of rough terrain.

Estimating the second derivative is challenging due to uncertainty.

For example, at range, laser readings may be so sparse that significant information about the surface is missing.

Also, a high degree of precision is required in projecting laser readings.

This precision may be unavailable due to latency or error in the pose estimation. We model these sources of error as a multivariate polynomial.

Its coefficients are learned using the shock data as ground truth — the accelerometers are used to train the lasers.

The resulting classifier operates on individual laser readings from a road surface described by a 3D point cloud.

The classifier identifies sections of road where the second derivative is likely to be large.

Thus, the vehicle can slow down in advance, reducing the shock it experiences.

The algorithm is an evolution of one we used in the 2005 DARPA Grand Challenge.

We analyze it using data from that route.

Today I read a paper titled “Equitable Partitioning Policies for Mobile Robotic Networks”

How can you not like a paper that exploits the usefulness of the classic Lloyd algorithm.

The abstract is:

The most widely applied strategy for workload sharing is to equalize the workload assigned to each resource.

In mobile multi-agent systems, this principle directly leads to equitable partitioning policies in which (i) the workspace is divided into subregions of equal measure, (ii) there is a bijective correspondence between agents and subregions, and (iii) each agent is responsible for service requests originating within its own subregion.

In this paper, we design provably correct, spatially-distributed and adaptive policies that allow a team of agents to achieve a convex and equitable partition of a convex workspace, where each subregion has the same measure.

We also consider the issue of achieving convex and equitable partitions where subregions have shapes similar to those of regular polygons.

Our approach is related to the classic Lloyd algorithm, and exploits the unique features of power diagrams.

We discuss possible applications to routing of vehicles in stochastic and dynamic environments.

Simulation results are presented and discussed.

Today I read a paper titled “Various Types of Aesthetic Curves”

The abstract is:

The research on developing planar curves to produce visually pleasing products (ranges from electric appliances to car body design) and indentifying/modifying planar curves for special purposes namely for railway design, highway design and robot trajectories have been progressing since 1970s.

The pattern of research in this field of study has branched to five major groups namely curve synthesis, fairing process, improvement in control of natural spiral, construction of new type of planar curves and, natural spiral fitting & approximation techniques.

The purpose of is this paper is to briefly review recent progresses in Computer Aided Geometric Design (CAGD) focusing on the topics states above.

Today I read a paper titled “Vibrotactile Stimulus Frequency Optimization for the Haptic BCI Prototype”

The abstract is:

The paper presents results from a psychophysical study conducted to optimize vibrotactile stimuli delivered to subject finger tips in order to evoke the somatosensory responses to be utilized next in a haptic brain computer interface (hBCI) paradigm.

We also present the preliminary EEG evoked responses for the chosen stimulating frequency.

The obtained results confirm our hypothesis that the hBCI paradigm concept is valid and it will allow for rapid stimuli presentation in order to improve information-transfer-rate (ITR) of the BCI.

Today I read a paper titled “On the Covariance of ICP-based Scan-matching Techniques”

The abstract is:

This paper considers the problem of estimating the covariance of roto-translations computed by the Iterative Closest Point (ICP) algorithm.

The problem is relevant for localization of mobile robots and vehicles equipped with depth-sensing cameras (e.g., Kinect) or Lidar (e.g., Velodyne).

The closed-form formulas for covariance proposed in previous literature generally build upon the fact that the solution to ICP is obtained by minimizing a linear least-squares problem.

In this paper, we show this approach needs caution because the rematching step of the algorithm is not explicitly accounted for, and applying it to the point-to-point version of ICP leads to completely erroneous covariances.

We then provide a formal mathematical proof why the approach is valid in the point-to-plane version of ICP, which validates the intuition and experimental results of practitioners.

Today I read a paper titled “On the Dynamics of Human Proximity for Data Diffusion in Ad-Hoc Networks”

The abstract is:

We report on a data-driven investigation aimed at understanding the dynamics of message spreading in a real-world dynamical network of human proximity.

We use data collected by means of a proximity-sensing network of wearable sensors that we deployed at three different social gatherings, simultaneously involving several hundred individuals.

We simulate a message spreading process over the recorded proximity network, focusing on both the topological and the temporal properties.

We show that by using an appropriate technique to deal with the temporal heterogeneity of proximity events, a universal statistical pattern emerges for the delivery times of messages, robust across all the data sets.

Our results are useful to set constraints for generic processes of data dissemination, as well as to validate established models of human mobility and proximity that are frequently used to simulate realistic behaviors.

Today I read a paper titled “Anatomical Feature-guided Volumetric Registration of Multimodal Prostate MRI”

The abstract is:

Radiological imaging of prostate is becoming more popular among researchers and clinicians in searching for diseases, primarily cancer.

Scans might be acquired at different times, with patient movement between scans, or with different equipment, resulting in multiple datasets that need to be registered.

For this issue, we introduce a registration method using anatomical feature-guided mutual information.

Prostate scans of the same patient taken in three different orientations are first aligned for the accurate detection of anatomical features in 3D.

Then, our pipeline allows for multiple modalities registration through the use of anatomical features, such as the interior urethra of prostate and gland utricle, in a bijective way.

The novelty of this approach is the application of anatomical features as the pre-specified corresponding landmarks for prostate registration.

We evaluate the registration results through both artificial and clinical datasets

Registration accuracy is evaluated by performing statistical analysis of local intensity differences or spatial differences of anatomical landmarks between various MR datasets.

Evaluation results demonstrate that our method statistics-significantly improves the quality of registration.

Although this strategy is tested for MRI-guided brachytherapy, the preliminary results from these experiments suggest that it can be also applied to other settings such as transrectal ultrasound-guided or CT-guided therapy, where the integration of preoperative MRI may have a significant impact upon treatment planning and guidance.

Today I read a paper titled “Automation of Mobile Pick and Place Robotic System for Small Food Industry”

The abstract is:

The use of robotics in food industry is becoming more popular in recent years.

The trend seems to continue as long as the robotics technology meets diverse and challenging needs of the food producers.

Rapid developments in digital computers and control systems technologies have significant impact in robotics like any other engineering fields.

By utilizing new hardware and software tools, design of these complex systems that need strong integration of distinct disciplines is no longer difficult compared to the past.

Therefore, the purpose of this paper is to design and implement a micro-controller based on reliable and high performance robotic system for food / biscuit manufacturing line.

We propose a design of a vehicle.

The robot is capable of picking unbaked biscuits tray and places them into furnace and then after baking it picks the biscuits tray from the furnace.

A special gripper is designed to pick and place the biscuits tray with flexibility.

Today I read a paper titled “Adaptive Locomotion of Multibody Snake-like Robot”

The abstract is:

This paper represents an adaptive rhythmic control for a snake-like robot with 25 degrees of freedom.

The adaptive gait control is implemented in algorithmic way in simulation and on a real robot.

We investigated behavioral and energetic properties of this control and a dynamics of different body segments.

It turned out that despite using homogeneous generators, physical constraints have an inhomogeneous impact on neighbor body segments.

By analytical modeling of such dynamics, it may result in heterogeneous coupling of oscillators for a rhythmic control and impact scalability and synchronization effects of gait pattern generators.

Today I read a paper titled “Dynamical issues in interactive representation of physical objects”

The abstract is:

The quality of a simulator equipped with a haptic interface is given by the dynamical properties of its components: haptic interface, simulator and control system.

Some application areas of such kind of simulator like musical synthesis, animation or more general, instrumental art have specific requirements as for the “haptic rendering” of small movements that go beyond the usual haptic interfaces allow.

Object properties variability and different situations of object combination represent important aspects of such type of application which makes that the user can be interested as much in the restitution of certain global properties of an entire object domain as in the restitution of properties that are specific to an isolate object.

In the traditional approaches, the usual criteria are founded on the paradigm of transparency and are related to the impedance error introduced by the technical aspects of the system.

As a general aim, rather than to minimize these effects, we look to characterize them by physical metaphors conferring to haptic medium the role of a tool.

This positioning leads to firstly analyze the natural human object interaction as a simplified evolutive system and then considers its synthesis in the case of the interactive physical simulation.

By means of a frequential method, this approach is presented for some elementary configurations of the simulator

Today I read a paper titled “Speech animation using electromagnetic articulography as motion capture data”

The abstract is:

Electromagnetic articulography (EMA) captures the position and orientation of a number of markers, attached to the articulators, during speech.

As such, it performs the same function for speech that conventional motion capture does for full-body movements acquired with optical modalities, a long-time staple technique of the animation industry.

In this paper, EMA data is processed from a motion-capture perspective and applied to the visualization of an existing multimodal corpus of articulatory data, creating a kinematic 3D model of the tongue and teeth by adapting a conventional motion capture based animation paradigm.

This is accomplished using off-the-shelf, open-source software.

Such an animated model can then be easily integrated into multimedia applications as a digital asset, allowing the analysis of speech production in an intuitive and accessible manner.

The processing of the EMA data, its co-registration with 3D data from vocal tract magnetic resonance imaging (MRI) and dental scans, and the modeling workflow are presented in detail, and several issues discussed.

Today I read a paper titled “Light-field Microscopy with a Consumer Light-field Camera”

The abstract is:

We explore the use of inexpensive consumer light- field camera technology for the purpose of light-field mi- croscopy.

Our experiments are based on the Lytro (first gen- eration) camera.

Unfortunately, the optical systems of the Lytro and those of microscopes are not compatible, lead- ing to a loss of light-field information due to angular and spatial vignetting when directly recording microscopic pic- tures.

We therefore consider an adaptation of the Lytro op- tical system.

We demonstrate that using the Lytro directly as an oc- ular replacement, leads to unacceptable spatial vignetting.

However, we also found a setting that allows the use of the Lytro camera in a virtual imaging mode which prevents the information loss to a large extent.

We analyze the new vir- tual imaging mode and use it in two different setups for im- plementing light-field microscopy using a Lytro camera.

As a practical result, we show that the camera can be used for low magnification work, as e.g. common in quality control, surface characterization, etc.

Today I read a paper titled “Self-organized adaptation of a simple neural circuit enables complex robot behaviour”

The abstract is:

Controlling sensori-motor systems in higher animals or complex robots is a challenging combinatorial problem, because many sensory signals need to be simultaneously coordinated into a broad behavioural spectrum.

To rapidly interact with the environment, this control needs to be fast and adaptive.

Current robotic solutions operate with limited autonomy and are mostly restricted to few behavioural patterns.

Here we introduce chaos control as a new strategy to generate complex behaviour of an autonomous robot.

In the presented system, 18 sensors drive 18 motors via a simple neural control circuit, thereby generating 11 basic behavioural patterns (e.g., orienting, taxis, self-protection, various gaits) and their combinations.

The control signal quickly and reversibly adapts to new situations and additionally enables learning and synaptic long-term storage of behaviourally useful motor responses.

Thus, such neural control provides a powerful yet simple way to self-organize versatile behaviours in autonomous agents with many degrees of freedom.

Today I read a paper titled “A level-set-based method for fixing overhangs in 3D printing”

The abstract is:
3D printers based on the Fused Decomposition Modeling create objects layer-by-layer dropping fused material

As a consequence, strong overhangs cannot be printed because the new-come material does not find a suitable support over the last deposed layer

In these cases, one can add some support structures (scaffolds) which make the object printable, to be removed at the end

In this paper we propose a level-set method to create object-dependent support structures, specifically conceived to reduce both the amount of additional material and the printing time

We also review some open problems about 3D printing which can be of interests for the mathematical community